Many people believe that at the conclusion of Leroux's story, Erik was redeemed by Christine's kiss. Yet if you read further, after the kiss, Leroux says the following:

"It is all in keeping with this incredible and yet veracious story. Poor, unhappy Erik! Shall we pity him? Shall we curse him? He asked only to be "some one," like everybody else. But he was too ugly! And he had to hide his genius OR USE IT TO PLAY TRICKS WITH, when, with an ordinary face, he would have been one of the most distinguished of mankind! He had a heart that could have held the empire of the world; and, in the end, he had to content himself with a cellar. Ah, yes, we must needs pity the Opera ghost."

If Erik was completely and truly redeemed as the result of Christine's kiss, then why must we pity him? The correct reaction would be to rejoice with him. As a redeemed person, he would have been completely changed. His past would have been forgiven and that heart that held the empire of the world could have been used to do so. He could have atoned for his crimes and then went on to benefit humanity. Yet he did not. Instead he chose to die. So was he really redeemed in the end?

That's interesting.
Let's look at this from a different perspective. He says that he has tasted all the happiness that the world can offer. I think that by redeeming it's not necessarily meant that he is changed, because he did lie about Phillipe in the same chapter. I think it means that he's finally been redeemed for all the fault the world has caused him. Not necessarily his own actions, but the pain from the actions of others. In other words, Erik finally learns what it means to love and to be loved when he'd been stripped of it before.
We must pity him because of everything that he could have been. He was happy with his redemption, but he was still far from what he could have been.

On the other hand, maybe it was redemption at all. When Christine stood before him and consented to be his wife, Erik considered himself and humanity on even terms. The cruelty that both had inflicted to each other was cancelled out.

So you don't see this as a redemption then, but more of a coming to terms with himself?

Your Idea does make sense, yeah. I think that it merely depends on how you view it. Your idea makes complete sense because he dies after, but I still think that he walks out with more than just coming to terms with the world. He learns how to really love, which goes into what I said above. So both.

I will agree that Erik learns to love as well as the terrible price that love sometimes brings; just because he loves doesn't necessarily mean he's loved in return. So he does a good thing by letting Christine go so she can be with Raoul, her true love. But I'm not so sure that's really redemption, at least to me anyway. He still ends up murdering Count Philippe (and letting Raoul take the blame for that). The way I see it, for him to be really and truly redeemed, there should be a profound change in him, one that is good toward all humankind, not just Christine.

I will agree that Erik learns to love as well as the terrible price that love sometimes brings; just because he loves doesn't necessarily mean he's loved in return. So he does a good thing by letting Christine go so she can be with Raoul, her true love. But I'm not so sure that's really redemption, at least to me anyway. He still ends up murdering Count Philippe (and letting Raoul take the blame for that). The way I see it, for him to be really and truly redeemed, there should be a profound change in him, one that is good toward all humankind, not just Christine.

I was thinking about this thread today and came across some interesting symbolism. When Erik takes Christine down to his lair for the first time, he is singing the Ressurection of Lazerus. In the biblical story of the Ressurection of Lazarus, Jesus is moved by the weeping of the Jews and weeps himself. He proceeds to raise Lazarus from the dead, when all hope was lost.
After Erik is crying from Christine's kindness towards letting him kiss her, he begins to cry. Christine is deeply moved and cries herself out of compassion and cries "poor, unhappy Erik!" This compassion reminds Erik of his humanity, because in that moment, Christine has acknowledged that even though he was so horrible to her, he is worthy of compassion; and in that moment, Christine sees him as not a monster, not and angel, and not the Opera Ghost, but merely Erik. This realization of humanity compells Erik to release Christine, because he is finally accepted for himself and realizes that he cannot hurt someone as good as "brave and honorable" as Christine.
You could say that perhaps he let Christine go for practical purposes. He did acknowledge that he knew Christine loved Raoul, but he knew that when she decided to be his "living bride" or earlier. He intended Christine to stay with him even after that, not contemplating letting her go until she showed him compassion. Erik also mentions at one point that "all I wanted was to be loved for myself." And later, "If I am a monster, it is because society has made me so."
Jesus raises Lazarus even after the Jews believe that all hope is gone, yet through their faith Jesus is able to raise him. Erik believes that all hope is gone, and that society has made him a monster. But his faith that Christine (i.e. the potential Christine sees in him as she leaves for the first time, continuously playing the Ressurection of Lazarus) will be able to help him through her goodness allows her to show him that he is still human. He furthers this when he is pleading with Christine to marry him, promising that he would be "as gentle as a lamb" if she would love him for himself. In addition, note that Erik is described as a living corpse - something skeletal, as if this represented the monster Erik whose deformity had killed him.
To be clear, Erik's recognizing his humanity doesn't necessarily mean that he is a good person. All it requires is for him to recognize himself as human, and there is no evidence that he doesn't. He does, however, tell Christine to take the ring for her "poor, unhappy Erik." Yes, he's not happy. But he was still "given back" his humanity.
This is also a strong beauty and the beast story embedded into this. Because Christine was able to show him compassion, he sees himself not as a monster, but as a man...Christine saved Erik from considering himself a monster and only commiting bad actions. According to the Oxford dictionary, the definition of redemption is "The action of saving or being saved from sin, error, or evil."
As Erik considers himself human, or seeing himself as at terms with the world, is the act of him being saved from the sins he had done. That doesn't make him a good person, nor does it mean he wouldn't do anything bad in the future (aka Raoul's case), but he actually frees Raoul, lets them go, and offers to send Christine's belongings to the Persian. The fact that he realized he was capable of good after thinking all hope was lost is something that I would consider a great change.
Erik is saved from his consideration of himself as a monster by coming to terms with the himself - as you put it - by Christine's actions. I would actually argue that if the wrongs and rights are cancelled out, he really is nothing but human. As I said before, this doesn't mean that he wouldn't do wrong in the future. I do consider him redeemed.

Actually, Lazarus and his sisters, Martha and Mary, were close friends of Jesus. Jesus learns of Lazarus' illness, knows he has died, and hastens to get to his friend. When he gets there, there are mourners there. Jesus Himself weeps and then He raises Lazarus from the dead. A theory I have heard posed is this. Maybe Jesus raised Lazarus from the dead to spare His own grief because these were close friends of his. It actually makes sense, because Jesus was as human as the rest of us. If we had the power to do so, would we bring a loved one back to life? Why not?

I don't know that the story behind the song is evidence that Erik was moved to compassion. I think he liked religious music and was fascinated by the Catholic Mass. He's apparently very familiar with the requiem and wedding Masses, but not because he wants to be Catholic.

As for Christine, I think she is brave and honorable at one point and that's where Daroga's and Raoul's lives are concerned. Prior to that time, she resorts to lying and devious measures. I don't say that to malign her. I just don't see her sweet and innocent 100% of the time.

Actually, Lazarus and his sisters, Martha and Mary, were close friends of Jesus. Jesus learns of Lazarus' illness, knows he has died, and hastens to get to his friend. When he gets there, there are mourners there. Jesus Himself weeps and then He raises Lazarus from the dead. A theory I have heard posed is this. Maybe Jesus raised Lazarus from the dead to spare His own grief because these were close friends of his. It actually makes sense, because Jesus was as human as the rest of us. If we had the power to do so, would we bring a loved one back to life? Why not?

I don't know that the story behind the song is evidence that Erik was moved to compassion. I think he liked religious music and was fascinated by the Catholic Mass. He's apparently very familiar with the requiem and wedding Masses, but not because he wants to be Catholic.

As for Christine, I think she is brave and honorable at one point and that's where Daroga's and Raoul's lives are concerned. Prior to that time, she resorts to lying and devious measures. I don't say that to malign her. I just don't see her sweet and innocent 100% of the time.

That's up to interpretation then, but I don't want to get into it.
The fact that Erik plays that specific song not once, but twice is what cued me in.
What we do know is that Christine was moved by his tears, and that is what compelled him to let her go. Anyway, just my two cents.